This invention relates generally to fireplace accessories, and more particularly to devices adapted for use with an existing fireplace installation, for improving the heating efficiency thereof.
Various heat-extraction systems for fireplaces have been proposed in the past few years, and have met with only moderate success. Some devices incorporated hollow coal-cradling gratings through which air or water circulated. Blowers and the like were used with some prior units, while others employed natural convection.
One of the problems associated with virtually all prior installations was that the efficiency of the heat-extracting process was extremely low. With many of the forced air gratings which were used, the front of the fireplace had to be open, to provide the necessary convection. Under such circumstances, large quantities of air from the room were drawn up the chimney, only to be replaced by colder air which seeped into the room from the outside. The small amount of heat obtained from such gratings did not nearly compensate for the loss up the chimney. As a result, the overall heating capacity of such arrangements was low. Moreover, in systems where heat was extracted from the coals, as in the case of a circulating-air type grate, the combustion efficiency of the fire was diminished, since the useful heat which was being extracted from the coals lowered their temperature. This has been found to detract from the overall performance of the heating system, since less heat per pound of fuel is being produced.
Efforts to limit the flow of air from the room by the use of glass enclosures greatly increased the combustion efficiency of the fire, but with such arrangements most of the heat contained in hot gases from the fire was still being drawn up the chimney.
In cases where water was pumped into a casing contained in the firebox for heating, the external plumbing associated therewith was usually aesthetically unattractive, as well as representing substantial costs involved with installation and maintenance. Alteration of the physical layout of the fireplace proved to be a costly measure, and was best avoided, if at all possible.